Heat exchanger



Oct. 19, 1965 J. L. M. HOLMAN HEAT EXCHANGER 2 Sheets-Sheet 1 Filed Aug. 28, 1963 R o T m V N. M L N H O J H O L M A N A T T O R N E Y S- .Oct. 19, 1965 J. L. M. HOLMAN 3,212,570

HEAT EXCHANGER Filed Aug. 28, 1963 2 SheetsSheet 2 FIG. 5

INVENTOR JOHN L M. HOLMAN 1 BYi vL ATTORNEYS United States Patent C 3,212,570 HEAT EXCHANGER John L. M. Holman, Medary Township, La Crosse County, Wis., assignor to The Trane Company, La Crossc, Wis., a corporation of Wisconsin Filed Aug. 28, 1963, Ser. No. 305,140 8 Claims. (Cl. 165-162) This invention relates to heat exchange apparatus and more particularly to heat exchangers of the shell and tube type. More specifically, this invention relates to means for supporting relatively long heat exchange tubes within a heat exchange shell wherein the ends of the tubes are rigidly fastened in tube sheets which are in turn fixedly secured to the shell.

In heat exchangers of the above indicated type there exists two basic thermal expansion problems.

First, since the ends of the tubes are fixed relative to the ends of the shell and since the shell is relatively stiff compared to the tubes, any thermal elongation of the tubes, not compensated for by thermal elongation of the shell, must be taken up by bending or buckling of the tubes. An adverse side effect of this thermal elongation is tube failure due to touching and rubbing of tubes that buckle or bend in a random fashion. This is especially true where the tubes are emersed in a boiling solution which may impart further deformation and continuous motion to the tubes.

The second basic thermal expansion problem that exists in exchangers of the type described is that while heat exchange tubes are first being heated by heat exchange fluid entering one end, a greater thermal elongation of the tubes takes place momentarily at that one end. However, since that end is the first to be heated, it is also the first to expand in diameter, increasing in section modulus making that end more rigid. Since the rigid end of the tubes is responsible for the initial thermal elongation, the tube tends to buckle initially at the other end causing a longitudinal movement of the tubes through the tube supports resulting in further wear. This buckling may be so severe that the tube may jam in the tube supports. Further, since the tube buckles initially only adjacent the cold end, the lateral displacement of the tube at that point is necessarily large. This then requires the provision of a substantial clearance between the tube bundle and the shell to accommodate this end buckling.

One solution that has been applied to these expansion problems has been the provision of an expansible shell to elongate with the tubes. Another solution has been to separate the tubes sufliciently far so no touching is possible even under buckling conditions. Still more frequently, the heat exchanger is designed so as to permit one end of the tubes to float longitudinally.

The invention herein disclosed thus provides another such solution to the above mentioned expansion problems in shell and tube heat exchangers which I have found particularly useful in the concentrator heat exchange section of absorption refrigeration machines. Of course, the invention has utility in other heat exchangers, especially those where the tube sheets are fixed and the tubes are suspended in a boiling solution or otherwise caused to vibrate.

Thus, a main object of this invention is to provide a solution to the aforementioned thermal expansion problems in shell and tube heat exchangers having fixed tube sheets.

A more specific object of my invention is to provide a shell and tube heat exchanger having fixed tube sheets with one or more fixed tube supports intermediate thereof.

Another object of my invention is to provide a shell 3,212,570 Patented Oct. 19, 1965 and tube heat exchanger having fixed tube sheets with floating tube supports intermediate thereof.

A further object of this invention is to provide a heat exchanger of the type described with a plurality of intermediate fixed tube supports which permit substantially only longitudinal movement of the tubes, said heat exchanger further being provided with floating tube supports intermediate of said fixed tube supports which permit lateral movement of the tubes only as a group.

Another object of my invention is to provide a heat exchanger of the type described with floating tube supports which guide the buckling movement of the tubes in the horizontal plane.

Still a further object of my invention is to provide in a heat exchanger having fixed tube sheets and fixed tube supports with floating tube supports located approximately six-tenths of the distance from the tube sheet to the closest fixed tube support.

Otherobjects and advantages of the device will become more apparent as this specification proceeds to describe the invention with reference to the drawings in which like reference numerals are used to identify like elements throughout.

FIGURE 1 is a horizontal sectional view of the heat exchanger taken from above through the center thereof;

FIGURE 2 is a vertical sectional view taken at line 22 of FIGURE 1 showing a fixed tube support;

FIGURE 3 is a vertical section taken at line 3-3 of FIGURE 1 showing a floating tube support;

FIGURE 4 is an enlarged sectional view taken at line 4-4 of FIGURE 3 showing a portion of the guide arrangement for the floating tube support; and

FIGURE 5 is a view similar to FIGURE 1 showing a modified form of the invention.

Looking now to FIGURE 1, heat exchanger 10 is provided with a cylindrical shell 12. Within the shell at one end 14 thereof, hereinafter denoted as the hot end, is provided a tube sheet 16. At the other end 18 thereof within the shell 12, hereinafter denoted as the cold end, is provided a second tube sheet 20. Each tube sheet is fixed within the shell and makes a seal therewith as by welding or other applicable means, thus defining a heat exchange space therebetween.

Each tube sheet is provided with a plurality of tube receiving apertures 22. Heat exchange tubes 24 extend through the heat exchange space to the apertures in each tube sheet. For purposes of clarity, only a few tubes are actually shown. The tube ends are sealingly secured within the apertures 22 as by rolling, spinning, welding or any other appropriate method.

Passage of heat exchange fluid through the tubes is by way of an inlet header 25 having an inlet pipe 26 disposed at the hot end of shell 12. Heat exchange fluid such as steam enters inlet pipe 26 to header 25 and is distributed to the hot ends of tubes 24. The steam may be condensed in the tubes, the condensate being discharged into header 28 at the cold end. A condensate drain pipe 30 is arranged at the bottom of header 28 for egress of condensate therefrom.

Referring to FIGURES l4 inclusive, it will be seen that the heat exchange space is further defined by horizontal partition member 32 which extends between the tube sheets and the sides of the shell some distance above the bottom of the shell. For purposes of disclosing the present invention, no apertures are shown in the tube sheets below partition 32 and that space is here unused. However, if desired this space could be used for other heat exchange equipment such as the evaporator, condenser or absorber in the absorption machine example. Such modifications however do not constitute part of the present invention.

The heat exchange space above partition 32 in the URE 1.

present example is shown as having a brine inlet 34 for brine such as aqueous lithium bromide solution which is to be concentrated by evaporating a portion of the water therefrom. The concentrated brine leaves the heat exchange space via liquid outlet 36. Steam that has been evaporated from the brine may leave the heat exchange space via vapor outlet 38. The tubes 24 are placed sufliciently close that the boiling of the brine within the heat exchange space would ordinarily cause the tubes to vibrate and rub each other if not for the use of my novel tube support means, it being understood that thermal elongation of the tubes relative to the shell would ordinarily cause the tubes to buckle or bend in a random manner.

My novel tube support means for use with a heat exchanger with fixed tube sheets comprises a plurality of fixed tube supports longitudinally spaced at equal intervals within the'heat exchange space. Each fixed tube support is comprised of a vertical plate having a plurality of apertures 42 in alignment with apertures 22 through which tubes 24 extend. Apertures 42 are bored to a size of .003 to .020 inch larger than the tube diameters in the unheated condition to accommodate thermal diametrical expansion, bending and longitudinal movement of the tubes therein. However, apertures 42 are sufliciently small to prevent any substantial lateral movement of the tubes therein.

Midway between each pair of fixed tube supports is arranged a floating tube support 44 which may be comprised of a vertical plate having apertures 46 similar to apertures 42. In addition a floating tube support of like construction is placed between each tube sheet and the fixed tube support closest thereto. It will be noted that these last mentioned floating tube supports are placed approximately six-tenths of the way from the tube sheet to the closest fixed tube support. The reason -for this .particular construction Will be discussed in connection with the operation of the instant invention.

Each floating tube support slidably rests on partition member 32. A notch 48 is provided in both fixed and floating tube supports to provide a flow passage for the liquid brine as it is passed longitudinally through the heat exchange space. The movement of each floating tube support longitudinally of said shell may be limited by angle iron guides 50 disposed adjacent the bottom end on each side thereof and fastened to partition member 32 as best shown in FIGURES 3 and 4. Additional guides may be placed at the upper end of each floating tube support if found desirable or necessary.

Each floating tube support is then permitted to float laterally of the shell 12 in the horizontal plane. In the apparatus herein disclosed, this movement is limited only by the abutment of the floating tube support on the side wall of the shell 12. However, stops may be provided to limit this floating movement of the floating support to something less so no abutment of the shell will occur, if desired.

The operation of the device shown in FIGURES 1-4 will now be described. It should be understood that when the heat exchanger is in the cold condition, tubes 24 are substantially straight and can be removed for repair or replacement if necessary through header cover plates 51. In other words tubes 24 have a substantially straight configuration in their natural state, i.e. without external forces applied thereto. Owing to the fact that the tube sheets are fixed relative to the shell, the tubes will bend or buckle laterally when heated to take up the added length due to thermal elongation. Fixed tube supports 40 limit the lateral movement of the tubes individually and as a group. Floating tube supports limit the lateral movement of the tubes individually but permit the tubes as a group to move laterally in the horizontal plane. The

'net result is that the tubes individually and as a group will take the general form of a sine wave as seen in FIG- All random bending is eliminated. It should be noted that the fixed tube supports define the nodes of said wave while the floating tube supports are positioned at the points of maximum deflection or antinodes. The term node is intended to define only those points of inflection of the wave-like form wherein the direction of curvature is reversed. Of course the number of tube supports will depend upon many factors including tube length, temperatures and the permissible lateral displacement. Because of the cantilever efiect of the tubes rigid- 1y secured in the tube sheets, the point of maximum deflection of the end waves or undulations occurs closer to the fixed tube supports than the tube sheets. For this reason the end floating tube supports are arranged approximately six-tenths the distance from the tube sheets to the end fixed tube support.

Since the random buckling is now eliminated, intertube rubbing and consequent wear is also eliminated.

Now looking to FIGURE 5, it will be seen that a modified form of the invention .is shown wherein the spacing between the fixed tube supports 40a is progressively smaller in a direction away from the fixed tube support adjacent the hot end. As in the aforementioned form, the floating tube supports 44a are arranged midway between each pair of fixed tube supports. Also the end floating tube supports are placed closer to the end fixed tube supports than the tube sheets for the reasons hereinabove stated.

Now the reason for and the operation of this modified construction will be explained. When steam or other heating medium is first introduced into the relatively cold tubes, the expansion tends to take place primarily at the hot end, i.e., the end where the steam is introduced. This expansion is both diametrical and longitudinal. The diametrical expansion is believed to increase the section modulus of the tube or stiffen the tube at the hot end. Since the tube must buckle to accommodate its increased length and since it is stifier at the hot end, the tube will first buckle at the cold end. This has two damaging side efiects. The tubes tend to shift from the hot end to the cold end causing wear of the tubes as they move longitudinally through the tube supports. Secondly, since the buckle first occurs in one place at the cold end and is consequently necessarily large in amplitude, substantial clearance must be provided between the tube group or bundle and the shell of the heat exchanger. The modified form eliminates these problems by placing the fixed tube supports further apart at the hot end. Since each tube acts as a column and since the ease by which a column will buckle is dependent upon its length, the tubes are made to buckle first at the hot end where the elongation first takes place. The buckling then takes place progressively as the tube heats, the buckling taking place in that section of the tube where the elongation takes place. Since any given buckled section need take up only the elongation then developed in that section, the lateral displacement of the buckle is kept to a minimum, thus permitting a minimum clearance between the tubes and the shell. Further, since the elongation is taken up in that section or length of tubing where it is developed, little or no longitudinal shifting of the tube will result, thus reducing tube wear at the points or zones where it passes through the tube supports.

Although I have described in detail the preferred embodiment of my invention, I contemplate that many changes may be made without departing from the scope or spirit of my invention and I desire to be limited only by the claims.

I claim:

1. A heat exchange apparatus comprising an elongated shell; a first tube sheet secured adjacent one end of said shell in fixed relation therewith; a second tube sheet secured adjacent the other end of said shell in fixed relation therewith; a plurality of elongated heat exchange tubes, each extending within said shell from one tube sheet to the other tube sheet; each of said tubes having a substantially straight natural configuration; means sealingly securing the ends of said tubes to said tube sheets; first header means adjacent said first tube sheet for the distribution of heat exchange fluid into said tubes; second header means adjacent said second tube sheet for the collection of heat exchange fluid from said tubes; said first and second header means being in fluid communication through said tubes; means for the passage of a second heat exchange fluid to and from the space within said shell, between said tube sheets and surrounding each of said tubes; means disposed intermediate said first and second tube sheets for forming each of said elongated heat exchange tubes into a wave-like configuration upon thermal elongation relative to said shell; said last named means including a plurality of floating tube supports each disposed adjacent said plurality of elongated heat exchange tubes intermediate the nodes thereof and a fixed tube support disposed between said floating tube supports adjacent said plurality of elongated heat exchange tubes at a node thereof.

2. The apparatus as defined by claim 1 wherein means is operatively associated with each of said floating tube supports for substantially limiting, at the floating support,

relative lateral movement between said tubes while permitting said tubes to float as a group; and means operatively associated with said fixed tube support for substantially limiting, at said fixed tube support, relative lateral movement between said tubes and lateral movement of said tubes as a group while permitting said tubes to pivot.

3. The apparatus as defined by claim 2, wherein means is provided for substantially limiting the floating movement of said floating tube supports.

4. The apparatus as defined by claim 3- wherein said floating tube supports are substantially limited to movement in the horizontal plane in a direction transverse to said elongated shell.

5. A heat exchange apparatus comprising an elongated shell; a first tube sheet secured adjacent one end of said shell in fixed relation therewith; a second tube sheet secured adjacent the other end of said shell in fixed relation therewith; a plurality of elongated heat exchange tubes, each extending within said shell from one tube sheet to the other tube sheet; each of said tubes having a substantially straight natural configuration; means sealingly securing the ends of said tubes to said tube sheets; first header means adjacent said first tube sheet for the distribution of heat exchange fluid into said tubes; second header means adjacent said second tube sheet for the collection of heat exchange fluid from said tubes; said first and second header means being in fluid communication through said tubes; means for the passage of a second heat exchange fluid to and from the space within said shell, between said tube sheets and surrounding each of said tubes; means disposed intermediate said first and second tube sheets for forming each of said elongated heat exchange tubes into a wave-like configuration upon thermal elongation relative to said shell; said last named means including two floating tube supports each disposed adjacent said plurality of elongated heat exchange tubes intermediate the nodes thereof and at least one fixed tube support disposed between said floating tube supports adjacent said plurality of elongated heat exchange tubes at 6 a node thereof; each of said floating tube supports being disposed more closely to a fixed tube support than said tube sheets.

6. The apparatus defined by claim 5 wherein one of said floating tube supports is disposed approximately sixtenths of the distance from the adjacent tube sheet to the adjacent fixed tube support.

7. A heat exchange apparatus comprising: an elongated shell; a first tube sheet secured adjacent one end of said shell in fixed relation therewith; a second tube sheet secured adjacent the other end of said shell in fixed relation therewith; a plurality of elongated heat exchange tubes, each extending within said shell from one tube sheet to the other tube sheet; each of said tubes having a substantially straight natural configuration; means sealingly securing the ends of said tubes to said tube sheets; an inlet header disposed adjacent said first tube sheet adapted for the distribution of a heating medium into said tubes; an outlet header disposed adjacent said second tube sheet adapted for the collection of the heating medium from said tubes; said headers being in fluid communication through said tubes; means for the passage of a second cooler heat exchange medium and from the space within said shell, between said tube sheets and surrounding each of said tubes; means disposed intermediate said first and second tube sheets for forming each of said elongated heat exchange tubes into a wave-like configuration upon thermal elongation relative to said shell; said last named means including at least four fixed tube supports disposed between said tube sheets; the spacing between said fixed tube supports being progressively smaller in a direction from said inlet header for a heating medium toward said outlet header whereby each of said tubes is caused to first form said wave-like configuration in that portion which first undergoes thermal elongation upon introduction of the heating medium; each of said fixed tube supports being fixedly secured within said :shell and having means operatively associated therewith for limiting, at said fixed support, relative lateral movement between said tubes and lateral movement of said tubes as a group; floating tube supports disposed within said shell between said fixed tube supports; and means operatively associated with each floating tube support for limiting, at said floating tube support, relative movement between said tubes while permitting a greater lateral movement of said tubes as a group.

8. The device as defined by claim 7 wherein said means operatively associated with each floating tube support limits the lateral movement of said tubes as a group, at said floating tube support, to movement in the horizontal plane.

References Cited by the Examiner UNITED STATES PATENTS 1,788,386 1/31 Ehrhart 165-159 1,796,708 3/31 Grace 165159 2,519,084 8/50 Tull l-l59 FOREIGN PATENTS 394,864 7/33 Great Britain.

CHARLES SUKALO, Primary Examiner.

KENNETH W. SPRAGUE, Examiner. 

1. A HEAT EXCHANGE APPARATUS COMPRISING AN ELONGATED SHELL; A FIRST TUBE SHEET SECURED ADJACENT ONE END OF SAID SHELL IN FIXED RELATION THEREWITH; A SECOND TUBE SHEET SECURED ADJACENT THE OTHER END OF SAID SHELL IN FIXED RELATION THEREWITH; A PLURALITY OF ELONGATED HEAT EXCHANGE TUBES, EACH EXTENDING WITHIN SAID SHELL FROM ONE TUBE SHEET TO THE OTHER TUBE SHEET; EACH OF SAID TUBES HVAING A SUBSTANTIALLY STRAIGHT NATURAL CONFIGURATION; MEANS SEALINGLY SECURING THE ENDS OF SAID TUBES TO SAID TUBE SHEETS; FIRST HEADER MEANS ADJACENT SAID FIRST TUBE SHEET FOR THE DISTRIBUTION OF HEAT EXCHANGE FLUID INTO SAID TUBES; SECOND HEADER MEANS ADJACENT SAID SECOND TUBE SHEET FOR THE COLLECTION OF HEAT EXCHANGE FLUID FROM SAID TUBES; SAID FIRST AND SECOND HEADER MEANS BEING IN FLUID COMMUNICATION THROUGH SAID TUBES; MEANS FOR THE PASSAGE OF A SECOND HEAT EXCHANGE FLUID TO AND FROM THE SPACE WITHIN SAID SHELL, BETWEEN SAID TUBE SHEETS AND SURROUNDING EACH OF SAID TUBES; MEANS DISPOSED INTERMEDIATE SAID FIRST AND SECOND TUBE SHEETS FOR FORMING EACH OF SAID ELONGATED HEAT EXCHANGE TUBES INTO A WAVE-LIKE CONFIGURATION UPON THERMAL ELONGATION RELATIVE TO SAID SHELL; SAID LAST NAMED MEANS INCLUDING A PLURALITY OF FLOATING TUBE SUPPORTS EACH DISPOSED ADJACENT SAID PLURALITY OF ELONGATED HEAT EXCHANGE TUBES INTERMEDIATE THE NODES THEREOF AND A FIXED TUBE SUPPORTING DISPOSED BETWEEN SAID FLOATING TUBE SUPPORTS ADJACENT SAID PLURALITY OF ELONGATED HEAT EXCHANGE TUBES AT A NODE THEREOF. 